Conventionally, as an acoustic instrument vibrating plate made of plastic, there have been used acoustic instrument vibrating plates made of polyethylene terephthalate (PET) film, and also polyethylene naphthalate (PEN) or polyetherimide (PEI) having better heat resistance and rigidity than PET (see Patent documents 1, 2, and 3).
However, in the case where an acoustic instrument vibrating plate using PET is employed in a speaker of a small diameter, for example, for a cellular phone, thermal deformation easily occurs in an atmosphere at 65° C. or more, and heat resistance is not sufficient. On the other hand, an acoustic vibrating plate of PEN is better in heat resistance than a vibrating plate made of PET but still not sufficient in heat resistance. Further, regarding an acoustic vibrating plate of PEI, there have been problems that acoustic properties are deteriorated depending on a shape of speaker vibrating plate, and breakage of film occurs due to not withstanding a larger external power output. Therefore, an acoustic vibrating plate made of polyphenylene sulfide (PPS) excellent in heat resistance and mechanical properties has been proposed (Patent document 4), but moldability is not sufficient, there has been a problem that a film is broken in heat molding. Further, a film made of PPS and polyetherimide has been proposed (Patent document 5), but moldability is not sufficient and there has been a problem that a film is broken in heat molding.    Patent document 1: Japanese Unexamined Patent Publication No. 1-67099    Patent document 2: Japanese Unexamined Patent Publication No. 62-263797    Patent document 3: Japanese Examined Patent Publication No. 4-68839    Patent document 4: Japanese Unexamined Patent Publication No. 6-305019    Patent document 5: Japanese Unexamined Patent Publication No. 2001-261959